Zigzag Traversal

Spiral Traversal or Zigzag Traversal in a Tree.
This is the fourth article in the Tree Traversals - Online Classes.
Recently I wrote an article on Level Order Tree Traversal. Another problem on the same lines is to traverse the tree in a zigzag manner. That is also termed as spiral traversal. This question has been asked in many companies during the interview process.
Although it is not very specific problem, if you understand the idea behind traversing a tree in breadth first manner, then you can easily solve this. Please read further for more understanding.
Defining the problem
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